Mask-to-frame welding indicator

ABSTRACT

A mask-to-frame assembly apparatus for use in the manufacture of color television picture tubes, includes a curvilinear surface, having a plurality of electrical contacts disposed thereabout. A corresponding plurality of lamps coupled, respectively, between the shadow mask and the electrical contacts, are illuminated when the mask is properly engaged with the surface. The assembly apparatus further includes an electrical interlock, coupled to the lamps which permits energization of the mask-to-frame welding apparatus when the shadow mask is properly engaged.

United States Patent I [72] Inventor Robert Ploog [56] References Cited ff gldge, UNITED STATES PATENTS No. 1 103 5 1968 2,402,119 6/1946 Beggs 29/25.l5X [45] Patented 1971 3,309,493 3/1967 Vitale 29/25.13X [73] Assignee Corporation 3,351,996 11/1967 Fiore 29/25.15X

Chicago, 1]]. Primary Examiner-A. Bartis Assistant.ExaminerGeorge A. Montanye Attorney-Nicholas A. Camasto ABSTRACT: A mask-to-frame assembly apparatus for use in the manufacture of color television picture tubes, includes a curvilinear surface, having a plurality of electrical contacts [54] F INDICATOR disposed thereabout. A corresponding plurality of lamps coumung pled, respectively, between the shadow mask and the electri- [52] U.S.Cl. 219/109, cal contacts, are illuminated when the mask is roperly en- P 313/85, 29/25.l5 gaged with the surface. The assembly apparatus further in- [51] Int. Cl. 823k 9/10 cludes an electrical interlock, coupled to the lamps which per- [50] Field of Search 219/109; mits energization of the mask-to-frame welding apparatus 29/25.l5, 25.13, 471.1; 340/282, 471 when the shadow mask is properly engaged.

PATENIEU FEB 1 s IQYI FIG. 2

Invenfor 6 M 2 ma. my d MASK-TO-FRAME WELDING INDICATOR This invention relates to an improvement in the mask-toframe assembly apparatus used in the manufacture of color television picture tubes. The improvement provides means for indicating when the curvilinear shadow mask is properly positioned with respect to the frame in the assembly apparatus. A modification includes means for fastening the mask to the frame whenthe shadow mask is in proper position.

During tri-gun'picture tube operation an electron source, secured inside the neck of the picture tube, generates three electron beams, each corresponding to one of three primary colors. Portions of these beams pass through the shadow mask, impinging corresponding color phosphors deposited on the interior surface of the picture'tube faceplate. It is well known that in order to assure proper electron impingement, and thereby chromatic purity, the distance between the shadow mask and the faceplate must be held within very strict tolerances. This critical distance, known in the art as Q-spacing, is generally achieved by accurately positioning the frame and the shadow mask in conventional assembly apparatus, welding the mask to the frame, and ultimately securing the mask-frame combination to a plurality of mounting studs accurately disposed about the periphery of the faceplate.

The assembly apparatus comprises a fixture having a curvilinear surface, similar to the contour of the shadow mask, and a plurality of supporting pegs accurately placed around and above the surface. The spatial relationship between the supporting pegs and the curvilinear surface in the assembly apparatus simulates the configuration of the mounting studs and the shadow mask in a properly Q-spaced picture tube.

During manufacture, the shadow mask is frictionally fastened to a forwardly extending rim portion of the frame, which is subsequently secured to the supporting pegs in the assembly apparatus. Engagement means, comprising a plunger and magnets mounted under the curvilinear surface, substantially seat the mask with the surface. When so seated, the shadow mask is secured to the frame by welding. The maskframe combination is then removed from the assembly apparatus and used as a negative for depositing the different color phosphors on the faceplate and is ultimately sealed within the picture tube in its mounted position...

For purposes of rigidity, the frame generally includes a relatively wide border which precludes complete cooperation between the plunger surface and the shadow mask. As a result, the peripheral portions of the shadow mask may not always be pressed into intimate contact with the curvilinear surface. In particular, the corners of the shadow mask may not seat with the surface, and this condition is seldom detectable before the mask is welded to the frame. When such a mask-frame assembly is supported on the mounting studs in the picture tube, the spatial relationship between the mask and the glass panel, i.e., the Q-spacing, is incorrect, and the defect may remain unnoticed until after the expensive slurrying process, in which the color phosphors are deposited on the panel, is completed.

The apparatus of the invention provides means for detecting improper engagement between the mask and the curvilinear surface prior towelding, whereupon the mask may be adjusted while the defect is still correctable. Specifically, the invention includesa plurality of lamps coupled between the shadow mask and a corresponding number of electrical contacts fastened to the areas on the curvilinear surface underlying those portions of the shadow mask which have a tendency to remain unmated withthe surface. When the shadow mask is properly seated, the lamps are illuminated and the mask is welded to the frame in a conventional manner. In the event any corner areas of the shadow mask remain disengaged, however, one or more of the lamps will not light, depending upon the number of disengaged areas, indicating the need for adjustment.

An electrical interlock coupled between the indicator circuit and the welder, is provided in a modifiedform of the invention. The interlock permits energization of the welder only when the mask is properly engaged with the curvilinear surface.

Accordingly, the primary object of this invention is to provide improved mask-to-frame assembly apparatus for use in paratus, indicating means for signalling when the shadow mask is properly positioned in the assembly apparatus.

A further object of this invention is'to provide, for use with color television picture tube mask-to-frame assembly apparatus, a plurality of lamps which are illuminated when the mask is properly positioned in the assembly apparatus.

A feature of this invention resides in an electrical interlock between the indicating means and the mask-to-frame welding means which permits operation of the welding means only when the shadow mask is properly positioned in the assembly apparatus.

Another feature of this invention resides in the arrangement of the lamps in the indicating means in a pattern for clearly indicating which shadow mask comers are properly seated.

Other objects, features and advantages of this invention will become apparent upon reading the following description in conjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of color television picture tube mask-to-frame assembly apparatus incorporating the invention.

FIG. 2 is an enlarged perspective view of a portion of the assembly apparatus of FIG. 1, including portions of a mask and frame, partially cutaway.

FIG. 3 is a circuit diagram of the indicating device and electrical interlock m'echanism shown in FIG. 1.

Referring now to FIG. 1, a mask-to-frame assembly apparatus 10 comprises a metallic base 11, having a concave curvilinear surface 12. Surface 12 is very smooth, has a substantially rectangular shape, and is preferably coated with a thin electrically insulating film (not shown). A plunger 13 is movably secured above base 11 and has a surface 14 which is similar in shape, but smaller in size, to curvilinear surface 12. A plurality of electromagnets 18 are appropriately secured beneath surface 12. When energized, the electromagnets tend to attract and hold the corners of the permeable shadow mask (not shown) into engagement with the curvilinear surface.

Four electrical conductors 20, 30, 40, and 50, comprising thin pieces of metallic foil are respectively secured to surface 12 near the four comers thereof. Another foil conductor 60 is secured to a central portion of surface 12, preferably into an area beneath surface 14 of plunger 13. A number of wires connect these conductors to indicating means 70, housing four lamps 25, 35, 45, and 55, the purpose of which will be explained below.

Three upright standards 15 are accurately disposed about surface 12 and three supporting pegs l6, simulating the mounting studs in a color picture tube, are respectively attached to standards 15. Supporting pegs l6 cooperate with mounting springs secured to the shadow-mask frame (not shown) for holding the frame in place above surface 12. A detailed description of the spatial arrangement of the frame, springs and mounting studs, may be found in the copending application of Richard Cowles, et a1. Ser. No. 742,651, filed Jul.5, 1968. i

-A welding apparatus 17, having a plurality of sequentially operable electrodes 17a, is accurately positioned with respect 7 shadow mask 85, having a rearwardly extending lip 86 is adjustably held on rim 82 of the frame by frictional forces therebetween.

Apertured mounting springs 87 which may be attached to frame 83 through a bimetallic hinge as clearly described in the shadow mask 85 into engagement with curvilinear surface 1.2.

in so doing, contact is-made'between conductor 60 (and ideally between each of the other foil conductors 20-50) and the metal shadow mask. As the mask is pressed into engagement with surface 12, its lip 86 moves with respect to rim 82' of the frame which is firmly supported on pegs 16. The mask is designed with a large enough lip 86 to insure substantial overlying of rim 82 when properly positioned.

Referring now to FIG. 3, indicating means 70 are connected to a plug 76 which is adapted for connection to any conventional AC voltage source. A transformer has a primary winding 72 connected across plug 76, and low-voltage secondary winding 73 connected between conductor 60 and a common lead 75. Lamp 25 is connected between conductor 20 and common lead 75. Similarly, lamps 35, 45 and 55 are connected between common lead 75 and electrical conductors 30, 40 and 50, respectively.

When the frame with the mask frictionally secured thereto is secured to the supporting pegs in the assembly apparatus,

plunger 13 is lowered tomove the mask forward into engagement with conductor 60, which it will be recalled is under surface 14 of the plunger. If properly seated with curvilinear surface 12, the mask is also pressed into engagement with conductors 20-50. Y

'Thus, mask 85 completes a plurality of electrical circuits, including secondary winding 73, conductor 60, conductors 20-50, and lamps 25-55. The circuit-for lamp 25, for exampie, is typical and extends over winding 73, conductors 60 and 20, the portion of shadow mask bridging these conductors, and lamp 25. Illumination of lamps 25-55 indicates the mask is firmly seated with surface 12 and hence, accurately positioned with respect to the frame. The mask is welded to the frame in that position, and when ultimately secured to the mounting studs in the picture tube, proper Q-spacing will result.

in the event the shadow mask is impr'operly seated with curvilinear surface 12, i.e., the mask is not pressed into engagement with all of conductors 20-50, one or more of the circuits to lamps 25-55 will be incomplete, thereby preventing illumination of corresponding lamps. Nonillumination of any lamp indicates that an area of the mask is not properly seated with surface 12 and the mask should be'adjusted prior to welding. For example, if one corner of the shadow mask overlying a foil conductor is hot pressed into engagement therewith, no electrical contact with the maskis made and the lamp connected to that conductor will not light. Nonillumination of a lamp indicates that a mask adjustment is necessary which simply involves manually pushing the appropriate area of the shadow mask into proper engagement with surface 12. Further, after welding and upon retraction of the plunger, the lamps provide quality control" information, whereby nonillumination of one or more of said lamps indicate the maskframe combination-may be defective.

. In accordance with a further aspect of the invention, lamps 25-55 are arranged in a pattern corresponding to the physical locations of conductors 20-50. Thus, lamp 25 corresponds to the left rear corner of the mask, lamp 35 to the left front, and so forth. Consequently, the machine operator can readily determine which area or areas of the mask are not properly seated by simple observation of the lamp configuration. Adjustment of the appropriate area or areas of the mask is thereby greatly simplified.

The preferred embodiment of the invention includes an electrical interlock for prohibiting energization of the welding apparatus until the indicating means indicate proper mask seating. The interlock comprises four relays 21, 31, 41 and 51. Relay 21 includes a normally open switch 22 and an electromagnet 23 connected in parallel with lamp 25. Similarly, relays 31, 4'1 and 51 include normally open switches 32, 42

and 52 and electromagnets 33, 43 and 53 connected in parallel with lamps 35, 45 and 55, respectively. Switches 22-52 are serially connected with welding apparatus 17 and. a manually operated start switch 74. Consequently, all must be e closed before the welding apparatus may be energized. Energization of the indicating lamps results in energization of the parallely connected electromagnets and consequent closure of their associated switches 21-51. Upon closure of manually operated start switch 74, power from the AC source to which plug 76 is connected flows to welding apparatus 17, causing electrodes 17a to sequentially operate and tack weld the shadow mask to the frame. If any of the switches remain open, indicating a mispositioned mask, the welding'apparatus cannot be energized.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Iclaim:

1. in combination: color television picture tube mask assembly apparatus having a first curvilinear surface; rigid frame means; a multiapertured metallic shadow mask, having a contour similar to said first curvilinear surface, adjustably retained on said rigid frame means; mounting means, accurately positioned with respect to said first curvilinear surface, supporting said frame means in predetermined alignment therewith; engagement means seating said shadow mask with said first curvilinear surface; and means, completing an elec and different ones of the rest of said regions, whereby said metallic shadow mask contacts said regions and completes" electric circuits from said voltage source to said lamps when said shadow mask is properly seated with said first curvilinear surface.

3. The combination as set forth in claim 2, wherein said first curvilinear surface comprises a metallic base having a nonconductive covering, and wherein each of said conductive regions comprises thin metallic foil, overlying said covering.

4. The combination as set forth in claim 3, wherein said frame means have a relativelywide border defining a window, and wherein said engagement means comprise a plunger having a second curvilinear surface smaller in size but similar in shape to said first curvilinear surface; said second surface being movable through said window for pressing said shadow mask into intimate contact with said first surface; peripheral areas of said shadow mask being untouched by said second surface and often assuming a nonmating relationship with said first surface and hence, being improperly seated therewith; said one conductive region secured in an area on said first surface engageable with said second surface to insure good electrical contact with said shadow mask; said rest of said conductive regions being located under said peripheral areas of said shadow mask.

5. The combination as set forth-in claim 4, wherein said assembly apparatus further includes fastening means operable for attaching said shadow mask to said frame means.

- 6. The combination as set forth in claim 5, wherein said fastening means includes means for welding said shadow mask to said rigid frame means when energized, and normally open switch means for energizing said welding means when said shadow mask is properly seated with said first curvilinear surface.

7. The combination as set forth in claim 6, wherein said normally open switch means include a plurality of' electromechanical relays each having a normally open contact set, each of said plurality of electromechanical relays being coupled in parallel with a respective one of said lamps, whereby each contact set is closed upon energization of its respective relay and consequent energization of its associated lamp.

8. In combination: color television picture tube assembly apparatus comprising a curvilinear surface having a plurality of conductive regions; a common lead; a plurality of lamps, electrically coupled between respective ones of said conductive regions and said common lead; a plurality of supporting pegs accurately positioned with respect to said curvilinear surface; a frame, having a forwardly extending rim, releasably secured to said supporting pegs; and electrically conductive shadow mask, having a lip portion overslipping said rim and being frictionally maintained thereon; engagement means, moving said shadow mask into seating engagement with said curvilinear surface, said lip portion'thereby sliding along said rim; voltage means, coupled betweensaid shadow mask and said common lead, whereby electric current flows through said mask into said conductive regions illuminating all of said lamps when said mask is properly seated with said curvilinear surface; and welding means operable to tack weld said lip to said rim.

9. The combination as set forth in claim 8, wherein said assembly apparatus further includes a plurality of relays for controlling operation of said welding means; said plurality of relays being individually coupled across said lamps each of said relays including a normally open switch serially connected in circuit with said welding means and said voltage means.

10. The combination as set forth in claim 9, wherein said conductive regions comprise thin pieces of metallic foil arranged in a pattern about said curvilinear surface; said lamps being arranged in a similar pattern, such that each lamp corresponds to an area on said surface underlying a corresponding piece of metallic foil, whereby. said lamps indicate the particular areas of nonengagement between said shadow mask and said curvilinear surface. 

1. In combination: color television picture tube mask assembly apparatus having a first curvilinear surface; rigid frame means; a multiapertured metallic shadow mask, having a contour similar to said first curvilinear surface, adjustably retained on said rigid frame means; mounting means, accurately positioned with respect to said first curvilinear surface, supporting said frame means in predetermined alignment therewith; engagement means seating said shadow mask with said first curvilinear surface; and means, completing an electrical circuit indicating said mask being in substantially complete engagement with said first curvilinear surface.
 2. The combination as set forth in claim 1, wherein said first curvilinear surface includes an array of electrically conductive regions; a first voltage source having one terminal coupled to one of said regions; and a plurality of lamps individually coupled between the other terminal of said first voltage source and different ones of the rest of said regions, whereby said metallic shadow mask contacts said regions and completes electric circuits from said voltage source to said lamps when said shadow mask is properly seated with said first curvilinear surface.
 3. The combination as set forth in claim 2, wherein said first curvilinear surface comprises a metallic base having a nonconductive covering, and wherein each of said conductive regions comprises thin metallic foil, overlying said covering.
 4. The combination as set forth in claim 3, wherein said frame means have a relatively wide border defining a window, and wherein said engagement means comprise a plunger having a second curvilinear surface smaller in size but similar in shape to said first curvilinear surface; said second surface being movable through said window for pressing said shadow mask into intimate contact with said first surface; peripheral areas of said shadow mask being untouched by said second surface and often assuming a nonmating relationship with said first surface and hence, being improperly seated therewith; said one conductive region secured in an area on said first surface engageable with said second surface to insure good electrical contact with said shadow mask; said rest of said conductive regions being located under said peripheral areas of said shadow mask.
 5. The combination as set forth in claim 4, wherein said assembly apparatus further includes fastening means operable for attaching said shadow mask to said frame means.
 6. The combination as set forth in claim 5, wherein said fastening means includes means for welding said shadow mask to said rigid frame means when energized, and normally open switch means for energizing said welding means when said shadow mask is properly seated with said first curvilinear surface.
 7. The combination as set forth in claim 6, wherein said normally open switch means include a plurality of electromechanical relays each having a normally open contact set, each of said plurality of electromechanical relays being coupled in parallel with a respective one of said lamps, whereby each contact set is closed upon energization of its respective relay and consequent energization of its associated lamp.
 8. In combination: color television picture tube assembly apparatus comprising a curvilinear surface having a plurality of conductive regions; a common lead; a plurality of lamps, electrically coupled between respective ones of said conductive regions and said common lead; a plurality of supporting pegs accurately positioned with respect to said curvilinear surface; a frame, having a forwardly extending rim, releasably secured to said supporting pegs; and electrically conductive shadow mask, having a lip portion overslipping said rim and being frictionally maintained thereon; engagement means, moving said shadow mask into seating engagement with said curvilinear surface, said lip portion thereby sliding along said rim; voltage means, coupled between said shadow mask and said common lead, whereby electric current flows through said mask into said conductive regions illuminating all of said lamps when said mask is properly seated with said curvilinear surface; and welding means operable to tack weld said lip to said rim.
 9. The combination as set forth in claim 8, wherein said assembly apparatus further includes a plurality of relays for controlling operation of said welding means; said plurality of relays being individually coupled across said lamps each of said relays including a normally open switch serially connected in circuit with said welding means and said voltage means.
 10. The combination as set forth in claim 9, wherein said conductive regions comprise thin pieces of metallic foil arranged in a pattern about said curvilinear surface; said lamps being arranged in a similar pattern, such that each lamp corresponds to an area on said surface underlying a corresponding piece of metallic foil, whereby said lamps indicate the particular areas of nonengagement between said shadow mask and said curvilinear surface. 